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Chapter 18.2: Bacteria. 1. Prokaryotes are unicellular organisms that do not have a nucleus or membrane-bound organelles. 2. They are classified into two kingdoms-- archaebacteria and eubacteria .
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1. Prokaryotes are unicellular organisms that do not have a nucleus or membrane-bound organelles.
2. They are classified into two kingdoms-- archaebacteria and eubacteria.
3. There are three types of archaebacteria that live mainly in extreme habitats where there is usually no free oxygen available.
4. One type of archaebacterium lives in oxygen-free environments and produce methane gas.
5. A second type lives only in water with high concentrations of salt.
6. The third type lives in the hot, acidic water of sulfur springs.
7. Eubacteria, the other kingdom of prokaryotes, include those prokaryotes that live in places more hospitable than archaebacteria inhabit.
8. Some bacteria are parasites, obtaining their nutrients from living organisms
9. Others are saprobes--organisms that feed on dead organisms or organic wastes.
10. Some eubacteria live in places with sunlight because they need light to make the organic molecules that are their food.
11. Some eubacteria break down and release the energy of inorganic compounds containing sulfur and nitrogen in the process called chemosynthesis.
13. Prokaryotic cells have ribosomes, but they are smaller than those of eukaryotes.
14. They also have genes that are located in a single circular chromosome.
15. One structure that supports and protects a bacterium is the cell wall.
17. In 1928, Sir Alexander Fleming accidentally discovered penicillin, the first antibiotic--a substance that destroys bacteria.
18. Biologists discovered that penicillin can interfere with the ability of some bacteria to make cell walls.
19. The three most common shapes of bacteria are spheres called cocci; rods called bacilli; and spirals called spirilli.
20. Bacterial cells often grow in characteristic patterns that provide another way to categorize them.
21. Diplo- is a prefix that refers to a paired arrangement of cell growth.
22. The prefix staphlo- describes an arrangement of cells that resemble grapes.
23. Strepto- is a prefix that refers to an arrangement of chains of cells.
24. Bacteria reproduce asexually by a process known as binary fission.
26. Some bacteria have a form of sexual reproduction called conjugation.
27. During conjugation, one bacterium transfers its chromosome to another cell through a bridgelike structure called a pilus that connects the two cells.
28. Conjugation results in a bacterium with a new genetic composition.
29. Many bacteria require oxygen for respiration. These bacteria are called obligate aerobes.
30. There are other bacteria, called obligate anaerobes, that are killed by oxygen.
31. Some bacteria, when faced with unfavorable environmental conditions, produce endospores.
32. An endospore is a tiny structure that contains a bacterium’s DNA, encased by a tough outer covering that resists drying out, temperature extremes, and harsh chemicals.
33. When environmental conditions improve, the endospore germinates, or produces a cell that begins to grow and reproduce.
34. Some bacteria produce a powerful and deadly poison, called a toxin, as they grow.
35. Disease-causing bacteria are few compared with the number of harmless and beneficial bacteria on Earth.
36. Several species of bacteria have enzymes that convert nitrogen gas into ammonia in a process known as nitrogen fixation. Bacteria are the only organisms that can perform these chemical changes.
37. Life could not exist if decomposing bacteria did not break down the organic materials in dead organisms and wastes, returning nutrients to the environment.
38. Some foods that you eat would not exist without bacteria.
40. Bacteria also inhabit your intestines and produce vitamins and enzymes that help digest food.
41. Some bacteria produce important antibiotics that destroy other types of bacteria.
43. Bacterial diseases harm people in two ways. The growth of the bacteria can interfere with the normal functioning of body tissue, or it can release a toxin that directly attacks the host.
